The subject matter described herein relates generally to methods and systems for wind turbines, and more particularly, to methods and systems regarding the power generator of a wind turbine, even more particularly, the stator of a wind power generator and the positioning of the power converter.
Large scale wind turbines that feed electrical power into electrical supply grids have been growing rapidly in recent years. This growth rate can be traced back to the many environmental, technical and economic benefits and improvements of wind energy technologies. Wind energy enables a reduction in use of fossil fuels as energy source, which consequentially reduces the production of greenhouse gases. Furthermore, wind energy is widely available, renewable and clean. Technical developments have improved design, manufacturing technologies, materials and power electronic devices of wind turbines that enable the production of robust and efficient wind turbines at lower costs.
Generally, a wind turbine includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Some wind turbine configurations include double-fed induction generators (DFIGs). Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency. Moreover, such converters, in conjunction with the DFIG, also transmit electric power between the utility grid and the generator as well as transmit generator excitation power to a wound generator rotor from one of the connections to the electric utility grid connection. Alternatively, some wind turbine configurations include, but are not limited to, alternative types of induction generators, permanent magnet (PM) synchronous generators and electrically-excited synchronous generators and switched reluctance generators. These alternative configurations may also include power converters that are used to convert the frequencies as described above and transmit electrical power between the utility grid and the generator.
In some known wind turbines, the nacelle of a wind turbine contains the essential machinery and power electronic devices that enable the efficient conversion of wind energy into electrical energy such as the generator and possibly the power converter. Sometimes, the converter is in the lower part of a wind turbine tower. As heart of a wind turbine, the nacelle must function reliably and cost efficiently throughout the service life of the wind turbine. Usually, the space inside the nacelle is limited and a high number of power cables or bus-bars are used to connect the individual power electronic components, which add costs.
Furthermore, known wind turbines have a plurality of mechanical and electrical components, which may have independent or different operating limitations, such as current, voltage, power, and/or temperature limits, than other components. Since, many of the electrical and/or mechanical components come together for the first time after being installed in the wind turbine, known wind turbines typically are designed and/or assembled with predefined rated power limits. To operate within such rated power limits, the electrical and/or mechanical components may be operated with large margins for the operating limitations. Such operation may result in inefficient wind turbine operation, and a power generation capability of the wind turbine may be underutilized.
For this purpose, it will be appreciated that easy testing of the mechanical and power electronic components before installation, to ensure an optimum compatibility between the components and an efficient, harmonious, long-lasting and trouble-free operation of the wind turbine is desired. Further, easy repair and exchange of faulty parts as well as the reduction of material costs inside the nacelle and an increase in overall efficiency of the wind turbine is desirable.
Hence, the subject matter described herein pertains to improved assembly methods and systems, in particular with respect to power generators and power converters, in order to achieve the aforementioned cost, reliability, spatial, material and maintenance benefits.